Modern two-way radio messaging systems have begun to utilize antenna beamforming techniques to improve inbound reception sensitivity and to increase capacity under certain conditions. These techniques have allowed inbound transmissions to occur on the same time/frequency channel at smaller geographic separations than possible with omnidirectional receiver antenna patterns. However, the ability of the beamformer processor to optimize the beam direction for a transmission from a portable subscriber unit requires that the portable subscriber unit not be moving too fast relative to the beamforming antenna.
At times, the portable subscriber unit may be moving at highway speeds. Under this condition the portable subscriber unit can experience difficulty with inbound communications in systems designed for time/frequency reuse with beamforming based on a static assumption. Message loss can occur, because the beamforming processor cannot track the rapid phase changes that result from the movement.
Thus, what is needed is a method and apparatus that provides the advantages of beamforming techniques for improving inbound sensitivity and increased capacity, while also providing an ability to adapt itself to subscriber units moving rapidly with respect to the beamforming antenna. Preferably, the method and apparatus will be operable with existing two-way subscriber units in the field.